For safety reasons, tractors, lawn and garden vehicles, riding mowers and other off road vehicles may be provided with some form of rollover protection system, or ROPS, to prevent the vehicle from crushing the operator if it accidentally rolls over. The ROPS should be capable of supporting the forces generated by the weight of the vehicle in the event of a rollover, maintaining free space for the operator to reduce the danger of injury.
If a cab is provided, the ROPS may be built into the cab. If a cab is not provided, the ROPS may consist of a generally U-shaped crossbar located above the head of the operator, and legs connected to the vehicle frame.
The ROPS may be straight tubing, and the legs or lower section of the ROPS may be welded to brackets and/or bolted to the vehicle frame. A ROPS is designed to absorb energy from the weight of the vehicle, and the brackets or lower section of the ROPS may transfer energy to the vehicle frame.
Some ROPS may be folded down from a raised or upright position to a lowered or folded down position. For example, U.S. Pat. Nos. 4,949,991; 5,503,430; 5,779,272; and 5,839,758 relate to ROPS that can be moved from a raised or upright position to a lowered or folded down position. The hinge assembly where the ROPS structure folds may be a rotary style joint that may be easily and quickly operated between the raised and lowered positions without tools. Retention or locking pins (e.g., rods, clips or bolts) may be inserted through holes or slots in the upper and lower ROPS, and/or through holes in hinge plates joining the upper and lower ROPS. If the retention or locking pins become loose, especially due to wear of the ROPS system, the gap between the pin and hole allows the ROPS to rattle during use. Clearances between parts including brackets, ROPS tubing and pins may be dictated by manufacturing requirements and must be relatively loose to provide a cost effective ROPS that may be easily assembled and operated. However, the clearances may result in rattling of the ROPS especially in the raised position.
There have been several attempts to solve the rattle problem. For example, tighter clearances may be required between the parts to prevent rattling, or a knob on the ROPS can be tightened to provide tension on the joint. Other examples include U.S. Pat. No. 7,568,732 for a ROPS with cushions within the hinges that take up slack in the system to minimize rattling when the structure is locked in its use position; U.S. Pat. No. 7,661,709 for a vibration dampening system for overhead frame structures; and U.S. Pat. No. 7,971,905 for a folding ROPS with a resilient wedge-shaped member that isolates the upper ROPS from the lower ROPS.
A folding ROPS is needed with vibration dampeners that can isolate the upper ROPS from the lower ROPS without rattling during use. A folding ROPS with vibration dampeners is needed that may be easily folded and locked in a raised or lowered position without tools.